Problem: Subtract.
There are many ways to solve this problem. Let's see two ways we can solve it. Place Value We can think in terms of tenths: $\begin{aligned} &\phantom{=}7- 5.8\\\\ &=7.0- 5.8\\\\ &=70\text{ tenths} -58\text{ tenths}\\\\ &=12\text{ tenths}\\\\ &=1.2 \end{aligned}$ Place value table Let's line up the numbers by their decimal places. Ones $.$ Tenths ${7}$ $.$ $0$ ${5}$ $.$ $8$ Now, let's subtract each place value column. Ones $.$ Tenths $\overset{6}{\cancel{{7}}}$ $.$ $\overset{10}{\cancel{0}}$ $-$ $5$ $.$ $8$ $\underline{~~~~}$ $\underline{~~~~}$ $1$ $.$ $2$ $1.2 = 7 - 5.8$